Objective　To evaluate the use of gabapentin in preemptive analgesia for adenotonsillectomy in children with obstructive sleep apnea hypopnea syndrome (OSAS). Methods　Eighty OSAHS patients, American Society of Anesthesiologists (ASA)Ⅰ or Ⅱ, undergoing adenotonsillectomy were divided into two groups, according to a random number table:an observation group or a control group, with 40 patients in each group. Patients in the observation group were orally administered with gabapentin 30 mg/kg 3 h before entry in the operation room. In the control group, placebo was given 3 h before entry in the room. All patients received patient controlled intravenous analgesia (PCIA) with fentanyl, where 8 μg/kg fentanyl was diluted to 50 ml. The initial dose was 4 ml, without background dose, and the bolus was 2 ml, with a lockout time of 30 min. The bolus would be adjusted to 3 ml, if analgesia was inadequate 2 h later. Those with vomiting were intravenously injected with 0.1 mg/kg granisetron. The Children's and Infants Postoperative Pain Scale (CHIPPS) scores and the consumption of fentanyl were recorded 1, 2, 4, 8, 16 h and 24 h after surgery. The adverse reactions of both groups were recorded. Results　The CHIPPS scores 1, 2, 4, 8, 16 h and 24 h after surgery and fentanyl doses were significantly lower in the observation group than those in the control group (P<0.05). Patients in the observation group reported less incidences of nausea, vomiting, anxiety and itching than the control (P<0.05). Conclusions　The use of gabapentin in preemptive analgesia for adenotonsillectomy in children with OSAS can effectively relieve postoperative pain and reduce the consumption of opioids after operation.